8.8 Rear Diff Fluid Question
 

I had to pull my axles to install longer studs. My question is does synthetic diff fluid already have the friction modifier added? And should I use 75-90 or 75-140?

75/90, and most do have an additive for limited slip rears, read the back of the bottle, valvoline and Royal purple both do I know

Thanks mjr

I still add the limited slip additive.